A typical configuration for a multi-port distribution point (DP) is illustrated in the FIG. 1, which is a schematic block diagram of a typical configuration of a prior art multi-port distribution point, generally referenced 10. In such a configuration, data coming from the network side is terminated at an optical network termination (ONT) 12 and distributed to the subscribers (not shown) on the subscriber-side of the network through a switch hierarchy composed of an external switch 14 (G.999.1 Switch in FIG. 1) and an internal switch within the multi-port distribution point unit (DPU) i.e., chips 161, 162, 163, and 164 (4-DFE in FIG. 1). ONT 12 ally has only a single user network interface (UNI) to service the multiple subscriber ports. On the other hand, a DP may support a varying number of subscribers and consequently requires a scalable architecture that use multiple DPU chips to connect to the multiple subscriber lines. To connect a single ONT containing a single UNI port to multiple DPU chips requires a switch component that can switch the data stream to the respective DPU chip. The probler with this architecture is the switch component not only drives up the cost of the DPU but also the power-consumption.
To simplify the problem of switching traffic within a multi-port DPU chip, the ITU-T G.999.1 (or G.int) is used. This ITU-T (The International Telecommunication Union Telecommunication Standardization Sector) recommendation, originally specified as a framing sub-layer and interface specification to be used between digital subscriber line (DSL) and PHY layer transceivers (physical layer device), simplifies the switching logic by encoding the subscriber line port into the G.999.1 frame header. This allows for very simple switching logic that can easily be implemented in hardware. In addition, each subscriber line can run at a different physical layer rate. The G.999.1 recommendation also supports a data flow-control (DFC) (“backpressure”) mechanism that extends the normal Ethernet “PAUSE” flow-control scheme by allowing flow-control to be applied to the traffic destined to a single subscriber line rather than to all traffic as is implemented by Ethernet flow-control.
Given that the cost and power of a switch is directly related to the number of switch ports it supports and the speed of each port and in addition, within a DP each DPU chip needs to be fed by a high-speed (multi-gigabit) data link in order to support the gigabit traffic rates to each subscriber; one of the problems to be solved is low to feed multiple subscriber lines with data traffic sourced from a single ONT UNI port without requiring expensive/power-consuming switching.